Monday, November 25, 2013

The Dangers of Pesticides to Humans

A pesticide is any substance used to control pests (i.e., insects, vegetation, fungi, etc).[1] Environmental Protection Agency (EPA) has approved roughly 11,000 pesticides intended for use in agriculture, inside homes, on lawns, in hand soaps, on clothing and other consumer goods.[2-4]

Most pesticides control the pests by poisoning them.[25] In the namesake of protecting our foods, we have almost wiped insects, birds, and other animals out of existence. In an NPR report, it has found that we are so successful in controlling pests that we can see only cornstalks in Iowa corn fields, but nothing else, not even a bee.[5-7,40]

Unfortunately, pesticides can be poisonous to humans as well. Some are very poisonous, or toxic, and may seriously injure or even kill humans. Others are relatively non-toxic. In this article, we will cover what are the harms that pesticides can bring us.

Potential Dangers of Pesticides

Speaking the least, pesticides can irritate the skin, eyes, nose, or mouth. In addition, exposure to them may result in the following:[1, 8-15]
  • Reproductive effects
    • Effects on the reproductive system or on the ability to produce healthy offspring
  • Teratogenic effects
    • Effects on unborn offspring, such as birth defects
  • Carcinogenic effect
    • Produces cancer in living animal tissues
    • Chemicals used in agriculture could be responsible for the high incidence of cancer in farm workers such as cancers of the lip, stomach, brain, prostate, connective tissue, lymphatic, and hematopoietic system.
  • Oncogenic effects
    • Tumor-forming effects (not necessarily cancerous)
  • Mutagenic effects
    • Permanent effects on genetic material that can be inherited.
  • Neurotoxicity
    • Poisoning of the nervous system, including the brain
    • Researche have asserted a connection between exposure to high levels of pesticides and the development of ADHD[45]
  • Immunosuppression
    • Blocking of natural responses of the immune system responsible for protecting the body

Although the answers are still not clear, the scientific evidence is quickly mounting that pesticide use is associated with the development of serious adverse health effects. One mechanism that pesticides can wreak havoc on our health is via DNA methylation.

DNA Methylation[16-23]

Although pesticides are subject to extensive carcinogenicity testing before regulatory approval, pesticide exposure has repeatedly been associated with various cancers. This suggests that pesticides may cause cancer via nonmutagenicity mechanisms. The present study provides evidence to support the hypothesis that pesticide-induced cancer may be mediated in part by epigenetic mechanisms.[21,47]

Epigenetics[16,44,47] is the study of heritable changes in gene activity which are not caused by changes in the DNA sequence. Examples of mechanisms that produce such changes are DNA methylation and histone modification, each of which alters how genes are expressed without altering the underlying DNA sequence.

Scientists from Northwestern University have examined seven commonly used pesticides (i.e., fonofos, parathion, terbufos, chlorpyrifos, diazinon, malathion, and phorate) in vitro and found evidence suggesting pesticides may modify gene promoter DNA methylation levels, suggesting that epigenetic mechanisms may contribute to pesticide-induced carcinogenesis.[21]

Who Are the Most Vulnerable?

Pesticides are prevalent and exist in abundance in our foods and environments. For example, they have been found in the least suspected food items such as rice[27] and red wine.[28]

People exposed to higher levels of pesticides as part of their job – for example in industry or in farming - may be at slightly higher risk of certain cancers, particularly leukemia and lymphomas.[8] Besides agricultural workers and farmers, children are also vulnerable to synthetic pesticides. Their internal organs are still developing, they consume more food and drink per pound of body weight, and they spend much more time playing on floors or lawns, right where the chemicals settle and accumulate.[35] That's why AAP (American Academy of Pediatrics) makes recommendations to reduce children's exposure to pesticides.[30,31]

How to Reduce Exposure to Pesticides?

Health risks of pesticide can be simply put as:
As we cannot control toxicity, we can only reduce our risk by reducing the exposure of pesticides from two sources:
  • Foods
  • Environments.

To reduce the exposure of pesticides from foods, go get the Shopper's Guide to Pesticides in Produce from EWG (Environmental Working Group). You can find which food items are the most dirty (i.e., loaded with more pesticides) and which items are the least dirty. For the dirtiest food items, buy organics. Also, follow the washing advice in [36] to reduce the pesticide residues on your foods (however, you cannot wash off systemic pesticides).[29]

Pesticides applied on residential lawns migrate indoors. A study by the U.S. Environmental Protection Agency (EPA) found that residues from outdoor pesticides tracked in by pets and on people's shoes can increase the pesticide loads in carpet dust by as much as 400 times.[37] Another study shows that concentrations are often higher in house dust than in the soil that surrounds the house, even on farms.[33] Once inside homes where they're not subject to the normal degradation caused by sunlight and rain, pesticides can persist for years.

To reduce pesticide exposure from your living environment, reduce using pesticides on your lawns or gardens. Try IPM (Integrated Pest Management):[35]
  • Deciding what pest levels are acceptable to you
  • Preventing pests by working with Mother Nature
  • Ensuring that all the plants you want to keep are healthy
  • Identifying and monitoring pests
  • Taking control steps
  • Cultivating pest-repelling plants
  • Calling in the bug patrol:
    • Ladybugs
    • Green lacewings
    • Parying mantis
    • Syrphid flies
  • Bringing in birds
  • Maintaining and adding to diversity
  • Seeking out alternatives to synthetic poisons
  • Using biological pesticides
Also, before you step inside your house, take off shoes and leave them outdoors. If you have pets, wash their feet before let them go inside.


  1. Toxicity of Pesticides (Cornell University)
  2. Superficial Safeguards: Most Pesticides Are Approved by Flawed EPA Process (Natural Resources Defense Council)
  3. Pesticide Reregistration Status (EPA)
  4. A Loophole For Pesticides Puts Public’s Health At Risk (EWG)
  5. Cornstalks Everywhere But Nothing Else, Not Even A Bee (NPR)
  6. Pesticide toxicity to bees (Wikipedia)
  7. Pesticides Applied to Crops and Honey Bee Toxicity
    • Relative to other insect genomes, the honey bee genome is markedly deficient in the number of genes encoding detoxifica­tion enzymes.
    • Bee colony numbers have declined by 45% over the past 60 years.
  8. Pesticides and Cancer (Cancer Research UK)
  9. Pesticide Exposure May Contribute to ADHD (American Academy of Pediatrics)
  10. Pesticides on
  11. Banned Pesticide DDT Is Still Killing California Condors
  12. Pesticides used in South American GMO-based agriculture: A review of their effects on humans and animal models
  13. Birth defects caused by glyphosate, Andres Carrasco (Talked at UC Irvine)
  14. Glyphosate-Based Herbicides Produce Teratogenic Effects on Vertebrates by Impairing Retinoic Acid Signaling
    • The direct effect of glyphosate on early mechanisms of morphogenesis in vertebrate embryos opens concerns about the clinical findings from human offspring in populations exposed to GBH in agricultural fields.
  15. Pesticides and Food: Health Problems Pesticides May Pose (EPA)
  16. Epigenetics (Wikipedia)
  17. Methylation subtypes and large-scale epigenetic alterations in gastric cancer
    • Cancer-specific epigenetic alterations were observed in 44% of CpGs, comprising both tumor hyper- and hypomethylation.
    • Our results provide insights into the epigenetic impact of environmental and biological agents on gastric epithelial cells, which may contribute to cancer.
  18. Jones PA, Laird PW: Cancer epigenetics comes of age. Nat Genet 21:163-167, 1999
  19. Jones PA: The DNA methylation paradox. Trends Genet 15:34-37, 1999
  20. Epigenetic analysis of stomach cancer finds new disease subtypes (Duke-NUS Graduate Medical School)
    • Many of the methylation alterations were associated with significant changes in gene expression, suggesting that the methylation alterations may be functionally important in the development of gastic cancer.
  21. DNA methylation alterations in response to pesticide exposure in vitro
    • The present study provides evidence to support the hypothesis that pesticide-induced cancer may be mediated in part by epigenetic mechanisms.
  22. DNA Methylation and Cancer (Journal of Clinical Oncology)
  23. Singal R, Wang SZ, Sargent T, et al: Methylation of promoter proximal-transcribed sequences of an embryonic globin gene inhibits transcription in primary erythroid cells and promotes formation of a cell type-specific methyl cytosine binding complex. J Biol Chem 277: 1897-1905, 2002
  24. Nation's Pediatricians Warn Against Pesticides in Food (EWG)
  25. Pesticide (Wikipedia)
  26. Systemic Pesticides: Chemicals You Can’t Wash Off
  27. Arsenic in Rice (FDA)
  28. 滅芬諾 (Methoxyfenozide) 農藥 found in red wine (News; in Chinese)
  29. You cannot wash off systemic pesticides
  30. AAP Makes Recommendations to Reduce Children's Exposure to Pesticides (American Academy of Pediatrics)
  31. Nation's Pediatricians Warn Against Pesticides in Food (EWG)
  32. Sustaining the Earth by G. T. Miller
  33. R. Lewis et al., "Measuring and Reducing Exposure to the Pollutants in House Dust," American Journal of Public Health 85 (1995): 1168.
  34. Pesticide Action Network--Advancing alternatives to pesticides worldwide
  35. The Healthy Home by Dave Wentz and Dr. Myron Wentz
  36. Four Important Cleaning Tasks In Your Morning Routine (Travel to Health)
  37. R. Renner, "Curse This House," New Scientist, iss. 2289, May 5, 2001.
  38. 蔬果上残余农药 如何影响我们的健康 (in Chinese)
  39. Pesticides (Diabetes and the Environment)
  40. The Year the Monarch Didn’t Appear
    • A major cause is farming with Roundup, a herbicide that kills virtually all plants except crops that are genetically modified to survive it.
  41. Black Raspberries Protectively Regulate Methylation of Wnt Pathway Genes in Precancerous Colon Tissue
    • Black raspberries inhibit colonic ulceration and, ultimately, colon cancer partly through inhibiting aberrant epigenetic events that dysregulate Wnt signaling.
  42. The Hidden Truth About Peanuts: From Food Allergies to Farm Practices
    • It is common to see a conventional peanut crop sprayed with some type of pesticide every 8-10 days during the growing season.
    • Most of the peanuts consumed in the U.S. are now one of the most pesticide-contaminated snacks we eat.
  43. Toxic pesticides from GM food crops found in unborn babies
    • The research suggested the chemicals were entering the body through eating meat, milk and eggs from farm livestock which have been fed GM corn.
  44. Team reprograms social behavior in carpenter ants using epigenetic drugs
    • Epigenetic regulation has been observed to affect a variety of distinct traits in animals, including body size, aging, and behavior.
  45. Attention-Deficit/Hyperactivity Disorder and Urinary Metabolites of Organophosphate Pesticides
    • Scientists' findings support the hypothesis that organophosphate exposure, at levels common among US children, may contribute to ADHD prevalence. 
  46. Outside Variants Wired into Epigenetic Circuits That Can Boost Disease Risk
  47. Unexpected role for epigenetic enzymes in cancer
  48. Which Food Fights Cancer Better?  (Travel to Health)

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